In the manufacturing of electronic devices it is well known to mount electrical or electronic components to a PCB (printed circuit board) and to wave (or flow) solder the components to the board. Some of the components to be mounted to the PCB are more heat sensitive than others and they cannot withstand the high temperatures involved with the wave soldering process. As a consequence, these components are not initially placed on the PCB; rather, the other components are placed on the PCB and the PCB is wave soldered. Next, the heat sensitive components are placed on the PCB and are hand soldered into position.
This procedure has at least one drawback. During the initial wave soldering stage the holes that are to accept the heat sensitive components become blocked with solder. As a result, it is difficult, if not impossible, to insert the leads of the heat sensitive components.
To overcome this problem, a temporary solder resist is applied to the PCB, at those locations that components will not be soldered during the initial wave soldering step. After the wave soldering step, and before inserting the heat sensitive components, the temporary solder resist is removed. The heat sensitive components are then inserted and hand soldered.